The rolls of a spinning frame and the like used in the drafting system for attenuating a textile strand must possess long wearing characteristics and be free from tendency to rock on the shaft as may develop if there is excessive play in the bearing. The stability of the rolls of a textile drafting system is especially important since the strand, which must be positively controlled at all times, is relatively small and during the drafting process is traversed back and forth across the surface of the roll to prevent excessive wear, as may cause grooving of the roll. Any departure from true axial alignment of the roll results in improper handling of the yarn and loss or variation in the tension exerted by the roll upon the fibers of the strand which would produce thick and thin spots in the yarn as a result of uneven drafting.
Since the surface of a cot or other roll cover must be buffed down periodically in order to retain a true surface, it is sometimes necessary to replace the cot when it becomes excessively thin or worn as a result. It is therefore necessary to take the roll apart and it is desirable that the various parts may be assembled and disassembled conveniently. If ball bearings are used there is a tendency to wear a groove in the race or other surface containing the ball bearings. Such has a tendency to produce excessive shake or rock in the bearings.
In view of the hostile environment wherein such rolls operate, due to the lint laden atmosphere of the mill, it is important that the bearings be sealed against entry of the lint and dirt. Many efforts have been made to more nearly satisfy the requirements for such rolls. For example, U.S. Pat. No. Re. 24,687 illustrates a simplified construction wherein ball bearings are sealed within enlarged ends of a cot carrying sleeve. A more complicated construction wherein the length of the bearing surface is increased through the use of parallel rows of roller bearings is illustrated in U.S. Pat. No. 3,228,088.
Accordingly, it is an important object of the invention to minimize shake or rock in the rolls of a drafting system by providing a long area of bearing surface contact. Such a contact may be afforded by double roller bearings which may be readily installed in a simplified construction and which will provide stability while preventing excessive wear.
Another important object of the invention is to provide an improved seal or barrier against encroachment by the lint laden atmosphere of the mill.
Another important object of the invention is to provide a drafting system roll assembly of inexpensive rugged construction which may be readily assembled and disassembled.